Quantitative Method for Determining the Lateral Strength of Bacterial Adhesion and Application for Characterizing Adhesion Kinetics

A quantitative method for measuring the shear force required to detach individual adhered bacteria using atomic force microscopy (AFM) was developed. By determining the total compression of the cantilever during cell detachment events, a more accurate means of calculating the applied lateral force necessary to remove individual cells was achieved compared to previous methods. In addition, a tunable assay for monitoring the dynamics of <i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i> adhesion strength was employed. The accumulation of force measurements over time allowed for the characterization of adhesion strength kinetics. <i>P. aeruginosa</i> reinforced its adhesion to the surface at a rate 7-fold faster than for <i>S. aureus</i>; the average adhesion strength of <i>P. aeruginosa</i> was larger than that of <i>S. aureus</i> at corresponding time points. Adhered cells of the same species and strain demonstrated a range of adhesion forces that broadened with time, indicating that the change in adhesion strength does not proceed uniformly.